4,4&#39;-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanates)

ABSTRACT

The 4,4&#39;-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanates) of the general formula ##STR1## are new polyisocyanates for the production of PU systems with high chemical stability and good thermal stability.

This application is a 371 of PCT/EP95/03260 filed Aug. 16, 1995.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to4,4'-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanates) of thegeneral formula: ##STR2## in which R₁ means an alkyl group with 1 to 6 Catoms and R₂ means chlorine or an alkyl group with 1 to 6 C atoms, aprocess for preparing the said polyisocyanates, and the use of the saidpolyisocyanates in polyurethane (PU) systems.

PU systems are defined below as polyurethane systems that containurethane groups and/or urea groups.

BACKGROUND ART

Toluene-2,4-diisocyanate and/or toluene-2,6-diisocyanate, abbreviatedTDI, or diphenylmethane-4,4'-diisocyanate, abbreviated MDI, continue tobe of considerable importance as polyisocyanate components in theproduction of PU systems.

A major drawback of TDI is its high toxicity. Although the compound ishandled on an industrial scale with the most stringent safetyprecautions possible, it carries a considerable risk potential.

A complete switch to the less toxic MDI is also only conditionallypossible since MDI, owing to its high reactivity, can be processed withpolyols, but not with aromatic polyamines.

In addition, the PU systems that are based on TDI and MDI are limited,in terms of their temperatures of use, to a maximum of 100° C.

BROAD DESCRIPTION OF THE INVENTION

The object of this invention was consequently to develop polyisocyanatesthat are not highly toxic, have lower reactivity than MDI, and can beprocessed with the conventional and new PU processing process. The goalof developing chemically stable PU systems that can be used attemperatures of above 100° C. was associated with the object.

These objects are achieved with the polyisocyanates of theabove-mentioned general formula I according to the invention.

R₁ and R₂ mean a C₁ -C₆ -alkyl group which can be the same in meaning ordifferent and may suitably stand for methyl, ethyl, n- or i-propyl, n-,i- or t-butyl, pentyl and its isomers and hexyl and its isomers. R₁ andR₂ are preferably the same in meaning and stand for one of theabove-mentioned C₁ -C₄ -alkyl groups.

The preferred polyisocyanate is the4,4'-methylene-bis-(3-chloro-2,6-diethylphenylisocyanate) with themeaning of R₁ and R₂ are each ethyl.

The production of the polyisocyanates according to the invention iscarried out in the known way by reacting the corresponding polyaminewith phosgene or a phosgene-releasing compound, such as, di- ortriphosgene (cf., e.g., Ullmanns Encykl. d. techn. Chemie Ullmann'sEncyclopedia of Industrial Chemistry!, 4^(th) Edition, Volume 13, pp.351 ff).

The corresponding polyamines are described in European Application A 0220 641. 4,4'-Methylene-bis-(3-chloro-2,6-diethylaniline) (M-CDEA) isthe preferred polyamine.

The phosgenation is carried out suitably in the presence of an inertsolvent such as, toluene or chlorobenzene at elevated temperature. Thereaction generally proceeds virtually quantitatively.

The resulting polyisocyanates have a high purity.

The processing of the polyisocyanates according to the invention into PUsystems is carried out basically in a known way by reaction withcompounds with at least two hydrogen atoms that are active compared topolyisocyanates and optionally chain-lengthening agents and optionallyin the presence of commonly used catalysts and optionally otheradditives (cf. Saechtling, Kunststoff Taschenbuch Plastics Notebook!,24^(th) Edition, published in Carl Hauser Verlag, Munich 1989, pp. 429if).

It is also possible to use mixtures of the polyisocyanates according tothe invention with other aliphatic or aromatic polyisocyanates orprepolymers of polyisocyanates or prepolymers that are based on mixturesof polyisocyanates with aliphatic or aromatic polyisocyanates.

Suitable representatives of compounds with at least two hydrogen atomsthat are active compared to polyisocyanates are especially polyols, suchas, e.g., polyether polyols, polyester polyols, or other polyols, (e.g.,polycaprolactones). Suitable representatives of chain-lengthening agentsare polyamines, such as, e.g., the aromatic diamines MOCA, M-CDEA,mixtures of M-CDEA with aromatic or aliphatic diamines or polyols orisomer mixtures of dimethylthiotoluenediamine (ibid., p. 430, orEuropean Published Patent Application No. A 220,641).

In addition, all commonly used catalysts, such as,tetramethylbutanediamine (TMBDA), diazabicylooctane (DABCO), dibutyltindilaurate (DBTC) or organic heavy metal compounds, can be usedindividually or in combination with additives, such as, softeners,stabilizers, fireproofing agents, propellants, or fillers (ibid. p.430).

A great advantage of the polyisocyanates according to the invention liesin that fact that they can be processed in the standard PU processingprocesses, such as, the one-shot RIM process, the two-shot prepolymerprocess, or the two-shot direct process.

In accordance with the preferred use of polyisocyanates in thePU-elastomer sector or especially in the PU-casting elastomer sector,preference is given to the prepolymer process.

The polyisocyanates according to the invention are suitably used in apolyurethane system that can be produced by reacting a

a) 4,4'-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanate) of generalformula I with

b) compounds with at least two hydrogen atoms that are active comparedto isocyanates and optionally

c) chain-lengthening agents optionally in the presence of commonly usedcatalysts and optionally other additives.

Preferred is a polyurethane system that can be produced by reacting a

a) 4,4'-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanate) of generalformula I with

b) compounds with at least two hydrogen atoms that are active comparedto isocyanates, preferably as described above, and

c) an aromatic diamine as a chain lengthener in the presence of theabove-mentioned commonly used additives.

Especially preferably, a4,4'-methylene-bis-(3-chloro-2,6-dialkylaniline), especially the4,4'-methylene-bis-(3-chloro-2,6-diethylaniline), is used as an aromaticdiamine either individually or as a component of a mixture with otheraromatic or aliphatic diamines or with polyols, and4,4'-methylene-bis-(3-chloro-2,6-diethylphenyl-isocyanate) is used ascomponent a).

The PU systems that are produced on the basis of new polyisocyanatesaccording to the invention are distinguished by high chemical stabilitythat is unexpected in comparison to known PU systems and by atemperature of use of up to 180° C..

These PU systems according to the invention are therefore used mainly inthe PU-elastomer sector--especially in the casting-elastomer sector--forthe production of, e.g., rollers, wheels, roller coatings, insulators,seals, or sealing compounds. It is eminently possible, however, to usethe PU systems for spray-coating or for PU foams.

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE 1a Production of4,4'-methylene-bis-(3-chloro-2,6-diethylphenylisocyanate)

100 g (0.26 mmol) of 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline)was introduced into 1000 g of dichlorobenzene in an autoclave at roomtemperature. 57 g (0.58 mol) of phosgene was introduced into thissolution over a period of 30 minutes. The reaction mixture was stirredin a sealed autoclave at 80° C. for 1 hour. Then, it was depressurized,and the hydrochloric acid that was produced, the excess phosgene, andthe solvent were removed. In this case, the title product resulted in ayield of 110 g (98% of theory). Other data concerning the product is:

IR (KBr): 2288.1 cm⁻¹

¹ H-NMR (CDCl₃, 400 MHz) in ppm: 6.69 s, 2H; 4.12 s, 2H; 2.91 q, 4H,J=7.5 Hz; 2.59 q, 4H, J=7.6 Hz; 1.20 t, 6H, J=7.6 Hz; 1.15 t, 6H, J=7.5Hz.

EXAMPLE 1b

Analogously to Example 1a, but with the solvent toluene, the titleproduct was obtained in a yield of 109 g.

Examination of 4,4'-Methylene-bis-(3-chloro-2,6-diethylphenylisocyanate)in Comparison with Isocyanates from the Prior Art in PU Systems

1. Isocyanates Used

MCDE-I4,4'-Methylene-bis-(3-chloro-2,6-diethylphenylisocyanate)=compoundaccording to the invention

MDE-I 4,4'-methylene-bis-(2,6-diethylphenylisocyanate)=comparisonsubstance

MDI 4,4'-methylene-bis-phenylisocyanate=comparison substance

2. Production of Prepolymers (Component A)

Prepolymer 1 (Invention) Prepolymer based on polytetramethylene etherglycol (PTMG; Tetraethane 650, Du Pont), with a molecular weight of 650and MCDE-I

1850 g=4 mol of 94% MCDE-I was melted under nitrogen (N₂) at 80° C.,introduced into a reaction flask, and intimately mixed with 1300 g ofPTMG=2 mol over 30 minutes while being stirred. The PTMG is linear andwas dehydrated before addition to isocyanate for 1 hour at 100° C. andunder a vacuum of 2500 Pa. After the addition of PTMG was completed, itwas then stirred for 2 more hours at 90° C. under N₂.

A prepolymer with a content of 5.2% of free NCO groups was obtained.This prepolymer is referred to as "PTMG 650-MCDE-I."

Prepolymer 2 (Invention) Prepolymer based on polytetramethylene etherglycol (PTMG; Terathane 2000, Du Pont) with a molecular weight of 2000and MCDE-I

1234 g=2.67 mol of 95% MCDE-I was melted under N₂ at 80° C., introducedinto a reaction flask, and intimately mixed with 2133 g=1.066 of PTMGover 30 minutes while being stirred. The PTMG is linear and wasdehydrated before addition to isocyanate for 1 hour at 100° C. and undera vacuum of 2500 Pa. After the addition of PTMG was completed, it wasthen stirred for 2 more hours at 90° C. under N₂.

A prepolymer with a content of 3.96% of free NCO groups was obtained.This prepolymer is referred to as "PTMG 2000-MCDE-I."

Prepolymer 3 (Invention) Prepolymer based on polycaprolactone glycol(PCL; CAPA 220, Interox) with a molecular weight of 2000 and MCDE-I

1245 g=2.7 mol of 94% MCDE-I was melted under N₂ at 80° C., introducedinto a reaction flask, and intimately mixed with 2133 g=1.066 mol of PCLover 30 minutes while being stirred. The PCL is linear and wasdehydrated before addition to isocyanate for I hour at 100° C. and undera vacuum of 2500 Pa. After the addition of PCL was completed, it wasthen stirred for 2 more hours at 90° C. under N₂.

A prepolymer with a content of 3.92% of free NCO groups was obtained.The prepolymer is referred to as "PCL 2000-MCDE-I."

Prepolymer 4 (Comparison) Prepolymer based on PTMG (Terathane 2000, DuPont) with a molecular weight of 2000 and MDE-I

1158 g=3 mol of 94% MDE-I was melted under N₂ at 80° C., introduced intoa reaction flask, and intimately mixed with 2400 g=1.2 mol of PTMG over30 minutes while being stirred. The PTMG is linear and was dehydratedbefore addition to isocyanate for 1 hour at 100° C. and under a vacuumof 2500 Pa. After the addition of PTMG was completed, it was thenstirred for 2 more hours at 90° C. under N₂.

A prepolymer with a content of 4.32% of free NCO groups was obtained. Werefer to this prepolymer as "PTMG 2000-MDE-I."

Prepolymer 5 (Comparison) Prepolymer based on PCL (CAPA 220, Interox)with a molecular weight of 2000 and MDE-I

If the PTMG in prepolymer 4 is replaced by the same amount of PCL, aprepolymer with a content of 4.23% of free NCO groups is obtained underotherwise identical conditions. This prepolymer is referred to as "PCL2000-MDE-I."

Prepolymer 6 Prepolymer based on PCL (CAPA 220, Interox) with amolecular weight of 2000 and MDI.

400 g=1.6 mol of MDI was melted under N₂ at 60° C., introduced into areaction flask, heated to 80° C. and intimately mixed with 1000 g=0.5mol of PCL over a period of 10 minutes while being stirred. The PCL islinear and was dehydrated before addition to isocyanate for 1 hour at100° C. and under a vacuum of 2500 Pa. After the addition of PCL wascompleted, it was then stirred for 2 more hours at 80° C. under N₂.

A prepolymer with a content of 6.6% of free NCO groups was obtained.This polymer is referred to as "PCL 2000-MDI."

3. Component B

Component B is either the melted diamine* or the clear degassedsolution, cooled to processing temperature (80° C.), of the diamine ordiamine mixture in question in the corresponding polyol. In addition,the solutions in the polyol contain an organic bismuth compound (Coscat®83 catalyst from the CasChem. Inc., New Jersey) relative to the overallsystem (components A+B).

Ethacure 300, Albemarle Inc.

4. Preparation of the Test Piece

The prepolymer (component A) and the diamines (chain lengtheners;component B) were intimately mixed at a molar ratio of 1:0.95, i.e., NCOgroups to the sum of free OH and NH₂ groups, at 80° C. for 30 seconds,poured into a metal mold, preheated to 110° C., with inside dimensionsof 200*200*2 (in mm), and finally pressed at the start of gelling (potlife) in a press at 200 bar and 110° C.. After setting was completed(demolding time), it was demolded and subsequently tempered at 110° C.for 16 hours. Test pieces were punched out of the hardened elastomers.

5. Test Parameters

    ______________________________________                                        Hardness Shore A and Shore D                                                                      DIN 53505                                                 Tear resistance  N/mm!                                                                            DIN 53515                                                 Tensile strength  N/mm.sup.2 !                                                                    DIN 53504                                                 Tension at 100% elongation                                                                        DIN 53504                                                 Elongation at break %                                                                             DIN 53504                                                 ______________________________________                                    

                                      TABLE I                                     __________________________________________________________________________    RESULTS WITH DIAMINE M-CDEA (I)                                                          "Proportion                                                                   by weight"                                                                    of            Hardness/Room          Stress                        "I" in     comp. B       Temperature                                                                           Hardness/                                                                          Tear Tensile                                                                            at 100%                                                                            Elongation               Prepolymer                                                                          Comp. B                                                                            per 100                                                                             Pot                                                                              Demold-                                                                            Shore                                                                             Shore                                                                             175° C.                                                                     Resistance                                                                         Strength                                                                           Elongation                                                                         at                       No.   in Mol %                                                                           comp. Life                                                                             ing Time                                                                           A   D   Shore A                                                                             N/mm!                                                                              N/mm.sup.2 !                                                                       N/mm.sup.2 !                                                                      Break                    __________________________________________________________________________                                                         %                        1 (Invention)                                                                       100  21.0  2'00"                                                                            20'  99  69  99   --   --   --   --                       2 (Invention)                                                                       100  100   2'30"                                                                            20'  98  45       53.3 19.7 9.2  433                      2 (Invention)                                                                       66   40.0  2'00"                                                                            45'  91  33       47.7 18.3 5.2  809                      4 (Compar.)                                                                         100  18.2  3'00"                                                                            45'  97  43       47.7 8.6  7.5  388                      4 (Compar.)                                                                         66   44.0  7'30"                                                                            60'  91  28       35.0 15.0 4.5  854                      3 (Invention)                                                                       100  16.0  2'30"                                                                            20'  98  52  97   73.5 17.7 11.4 353                      3 (Invention)                                                                       66   38.0  2'30"                                                                            45'  92  37       59.4 25.7 5.7  593                      5 (Compar.)                                                                         100  18.7  5'00"                                                                            60'  98  45  95   64.2 12.1 9.2  440                      5 (Compar.)                                                                         66   45.0  5'10"                                                                            60'  92  32  --   50.2 22.8 5.1  750                      6 (Compar.)                                                                         66   72.0  19"                                                                               9'  88  --  --   64.0 35.1 --   --                       6 (Compar.)                                                                         100  30.0  20"                                                                               5'  98  55  --   74.0 25.6 --   --                       __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________    Results with the Diamino Mixture Luvocure MUT-HT from Lehmann & Voss          (II)                                                                          Weight              Hardness/Room                                                                              Tear       Stress at                         ratio of            Temperature                                                                           Hardness/                                                                          propagation                                                                         Tensile                                                                            100% Elongation                   Prepolymer                                                                          prepolymer:                                                                         Pot                                                                              Demold-                                                                            Shore                                                                             Shore                                                                             175° C.                                                                     Resistance                                                                          Strength                                                                           Elongation                                                                         at                           No.   comp. B                                                                             Life                                                                             ing Time                                                                           A   D   Shore A                                                                             N/mm!                                                                               N/mm.sup.2 !                                                                       N/mm.sup.2 !                                                                      Break %                      __________________________________________________________________________    2 (Invention)                                                                       100:20.5                                                                            2'00"                                                                            40'  97  46  95   60.9  17.2 9.1  510                          4 (Compar.)                                                                         100:22.0                                                                            4'30"                                                                            45'  97  40  93   50.2  13.9 7.0  754                          3 (Invention)                                                                       100:19.0                                                                            2'40"                                                                            40'  98  47  95   76.8  20.7 9.7  464                          5 (Compar.)                                                                         100:22.5                                                                            5'20"                                                                            60'  97  46  95   60.9  17.2 9.1  510                          __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________    Results with the Diamine-Isomer Mixture Ethacure 300 (2.4 and 2.6 Isomers     of                                                                            Dimethylthiotoluenediamine) from Albemarle Inc. USA                           Weight              Hardness/Room                                                                              Tear       Stress at                         ratio of            Temperature                                                                           Hardness/                                                                          propagation                                                                         Tensile                                                                            100% Elongation                   Prepolymer                                                                          prepolymer:                                                                         Pot                                                                              Demold-                                                                            Shore                                                                             Shore                                                                             175° C.                                                                     Resistance                                                                          Strength                                                                           Elongation                                                                         at                           No.   comp. B                                                                             Life                                                                             ing Time                                                                           A   D   Shore A                                                                             N/mm!                                                                               N/mm.sup.2 !                                                                       N/mm.sup.2 !                                                                      Break %                      __________________________________________________________________________    1 (Invention)                                                                       100:12.0                                                                            1'30"                                                                            13'  99  67  95   100.5 32.0 26.1 165                          2 (Invention)                                                                       100:9.6                                                                             3'30"                                                                            20'  95  41       48.8  35.4 7.4  525                          4 (Compar.)                                                                         100:10.2                                                                            6'20"                                                                            45'  93  33       31.6  13.1 5.9  658                          3 (Invention)                                                                       100:9.0                                                                             4'00"                                                                            20'  95  40       66.6  42.4 8.2  479                          5 (Compar.)                                                                         100:10.5                                                                            6'20"                                                                            60'  94  36       45.0  18.1 6.9  571                          __________________________________________________________________________

What is claimed is:
 1. A4,4'-Methylene-bis-(3-chloro-2,6-dialkylphenylisocyanates) of theformula: ##STR3## wherein R₁ means an alkyl group having 1 to 6 C atomsand R₂ means chlorine or an alkyl group having 1 to 6 C atoms. 2.4,4'-Methylene-bis-(3-chloro-2,6-diethylphenylisocyanate).
 3. A processfor the production of a4,4'-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanate) of theformula: ##STR4## wherein R₁ means an alkyl group having 1 to 6 C atomsand R₂ means chlorine or an alkyl group having 1 to 6 C atoms,comprising reacting 4,4'-methylene-bis-(3-chloro-2,6-dialkylaniline) ofthe formula: ##STR5## wherein R₁ and R₂ have the above-mentionedmeanings, with phosgene or a phosgene-releasing compound.
 4. A processcomprising using a4,4'-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanate) of theformula: ##STR6## wherein R₁ means an alkyl group having 1 to 6 C atomsand R₂ means chlorine or an alkyl group having 1 to 6 C atoms, for theproduction of a polyurethane system.
 5. The process according to claim 4wherein the compound of formula I is4,4'-methylene-bis-(3-chloro-2,6-diethylphenylisocyanate).
 6. Apolyurethane system that has been produced by reacting:(a) a4,4'-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanate) of theformula: ##STR7## wherein R₁ means an alkyl group having 1 to 6 C atomsand R₂ means chlorine or an alkyl group having 1 to 6 C atoms, with (b)compounds with at least two hydrogen atoms that are active compared toisocyanates and, optionally, (c) chain-lengthening agents, optionally inthe presence of commonly used catalysts and optionally other additives.7. The polyurethane system according to claim 6 that has been producedby reacting:(a) a4,4'-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanate) with (b) acompound having at least two hydrogen atoms that are active compared toisocyanates, and (c) an aromatic diamine as a chain-lengthening agent,optionally in the presence of commonly used catalysts and optionallyother additives.
 8. The polyurethane system according to claim 7 whereinthe aromatic diamine is a4,4'-methylene-bis-(3-chloro-2,6-dialkylaniline) or a mixture of a4,4'-methylene-bis-(3-chloro-2,6-dialkylaniline) with one or morearomatic or aliphatic diamines or a polyol.
 9. The polyurethane systemaccording to claim 8 wherein4,4'-methylene-bis-(3-chloro-2,6-diethylphenylisocyanate) and, as anaromatic diamine, 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) or amixture of 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) with one ormore aromatic or aliphatic diamines or a polyol, are used.
 10. Thepolyurethane system according to claim 7 wherein4,4'-methylene-bis-(3-chloro-2,6-diethylphenylisocyanate) and, as anaromatic diamine,4,4'-methylene-bis-(3-chloro-2,6-diethylphenylisocyanate) or a mixtureof 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) with one or morearomatic or aliphatic diamines or a polyol, are used.